This invention relates to a joint structure of friction wheel support components of a friction wheel continuously variable transmission such as a toroidal continuously variable transmission, and a link connecting them.
Tokkai He 9-291997 and Tokkai Hei 9-317837 which the Japanese Patent Office published in 1997 disclose a toroidal continuously variable transmission as one example of a friction wheel continuously variable transmission.
In this toroidal continuously variable transmission, torque is transmitted between an input disk and an output disk via a pair of power rollers which are friction wheels gripped by the input disk and output disk. The power rollers are respectively supported free to rotate by trunnions, and when a trunnion is driven in a perpendicular direction to the rotation axis of the input disk, the force which the power roller receives from the input disk and output disk varies, and the power roller varies its orientation around a trunnion shaft together with the trunnion. The orientation of the power roller is expressed as a gyration angle. A variation of the gyration angle of the power roller causes a variation in the radii of the contact points between the power roller, input disk and output disk, and a speed ratio, which is a ratio of the rotation speeds of the input disk and output disk, therefore varies continuously.
In order to synchronize the gyration angles of the pair of power rollers, the trunnions supporting the power rollers must be displaced in mutually opposite directions. For this reason, the upper ends of the trunnion shafts are joined by an upper link, and the lower ends are joined by a lower link. An engaging hole is formed in each link, and a spherical joint fixed to the outer circumference of the trunnion shaft engages with these engaging holes. The midparts of the upper link and lower link are respectively supported by pins, and the links pivot on the pins according to the axial displacement of the trunnion.
A load acts on the power roller gripped by the input disk and output disk in a direction tending to push it away from the rotation axis, and a force is exerted on the trunnion in the same direction.
A link has the role of holding the trunnion at a predetermined distance from the rotation axis against this load. Therefore, the farthest point on the outer circumference of the spherical joint from the pin is always horizontally pushed toward the engaging hole.
When the link pivots and inclines from the horizontal position, the acting point of the pushing force is offset from the center line of the link, and exerts a moment on the link. It is undesirable that this moment assists the inclination of the link so that the link collides with other components of the trunnion.
It is therefore an object of this invention to prevent the trunnion from exerting a moment that promotes a further inclination of the link, when the link inclines.
In order to achieve the above objects, this invention provides a joint structure which joins a link and a supporting shaft of such a friction wheel continuously variable transmission that comprises an input disk and output disk arranged on a rotation shaft, a pair of friction wheels gripped between the input disk and the output disk, and supporting members supporting the friction wheels.
Each of the supporting members comprises the supporting shaft perpendicular to the rotation shaft. The link connects one end of the supporting shaft of one of the supporting members to one end of the supporting shaft of another supporting member, and supporting the supporting members against an outward force exerted by the friction wheels in a direction away from the shaft. The link is supported by a pin so as to be free to pivot.
The joint structure according to this invention comprises a joint fitted to the supporting shaft, and an engaging hole formed in the link into which the joint is inserted. The engaging hole comprises an inner circumferential surface, the joint comprises an outer circumferential surface in contact with the inner circumferential surface, and the outer circumferential surface and inner circumferential surface have a longitudinal sectional shape such that the force exerted by the outer circumferential surface on the inner circumferential surface due to the outward force does not generate a moment assisting inclination when the link inclines.
The details as well as other features and advantages of this invention are set fourth in the remainder of the specification and are shown in the accompanying drawings.